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Digital Modulation Techniques in Communication Engineering

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31 diapositives · 435 Views · Jan 06, 2020

This lecture covers Differential Phase Shift Keying, Quadrature Phase Shift Keying, and Minimum Phase Shift Keying along with an introduction to Information Theory. Understanding different modulation techniques and channel capacity are key aspects discussed. The importance of non-coherent detection and encoding schemes are highlighted.

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Digital Modulation Techniques in Communication Engineering
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  1. Digital Modulation Technique Presented By: Amit Degada. Teaching Assistant, SV NIT, Surat.

  2. Goal of Today’s Lecture • Differential Phase Shift keying • Quadrature Phase Shift Keying • Minimum Phase Shift Keying • Introduction To Information Theory • Information Measure

  3. Differential Phase Shift Keying (DPSK) • Why We Require? • To Have Non-coherent Detection • That Makes Receiver Design • How can we do? • 0 may be used represent transition • 1 indicate No Transition

  4. DPSK Transmitter What Should We Do to make Encoder?

  5. DPSK Transmitter…………Modified

  6. Differentially Encoded Sequence

  7. DPSK Receiver

  8. Goal of Today’s Lecture • Differential Phase Shift keying • Quadrature Phase Shift Keying • Minimum Phase Shift Keying • Introduction To Information Theory • Information Measure

  9. Quadrature Phase Shift Keying (QPSK) • Extension of Binary-PSK • Spectrum Efficient Technique • In M-ary Transmission it is Possible to Transmit M Possible Signal M = 2n where, n= no of Bits that we Combine signaling Interval T= nTb In QPSK n=2 === > So M =4 and signaling Interval T= 2Tb

  10. Quadrature Phase Shift Keying (QPSK) • M=4 so we have possible signal are 00,01,10,11 • Or In Natural Coded Form 00,10,11,01 Binary Dibit 00 Binary Dibit 10 Binary Dibit 11 Binary Dibit 01 -135 -45 45 135

  11. QPSK Waveform 00 11 00 11 10 10

  12. QPSK Signal Phase

  13. Constellation Diagram

  14. Quadrature Phase Shift Keying (QPSK) The QPSK Formula ………………(1) Where, ϕ(t)=135,45,-45,-135 Simplifying Equation 1 This Gives the Idea about Transmitter design

  15. QPSK Transmitter

  16. QPSK Receiver

  17. Synchronization Circuit

  18. Goal of Today’s Lecture • Differential Phase Shift keying • Quadrature Phase Shift Keying • Minimum Phase Shift Keying • Introduction To Information Theory • Information Measure

  19. Minimum Shift Keying (MSK) • In Binary FSK the Phase Continuity is maintained at the transition Point. This type of Modulated wave is referred as Continuous Phase Frequency Shift Keying (CPFSK) • In MSK there is phase change equals to one half Bit Rate when the bit Changes 0 to 1 and 1 to 0.

  20. Minimum Shift Keying (MSK) Let’s take fc1 and fc2 represents binary 1 and 0 Respectively Similarly Where

  21. Minimum Shift Keying (MSK) • The MSK Equation where For Symbol 0 For Symbol 1

  22. Carrier Phase Coding For dibit 00

  23. Carrier Phase Coding For dibit 10

  24. Carrier Phase Coding For dibit 11

  25. Carrier Phase Coding For dibit 01

  26. Goal of Today’s Lecture • Differential Phase Shift keying • Quadrature Phase Shift Keying • Minimum Phase Shift Keying • Introduction To Information Theory • Information Measure

  27. Information Theory • It is a study of CommunicationEngineering plus Maths • A Communication Engineer has to Fight with • Limited Power • Inevitable Background Noise • Limited Bandwidth

  28. Information Theory deals with • The Measure of Source Information • The Information Capacity of the channel • Coding If The rate of Information from a source does not exceed the capacity of the Channel, then there exist a Coding Scheme such that Information can be transmitted over the Communication Channel with arbitrary small amount of errors despite the presence of Noise

  29. Goal of Today’s Lecture • Differential Phase Shift keying • Quadrature Phase Shift Keying • Minimum Phase Shift Keying • Introduction To Information Theory • Information Measure

  30. Information Measure • This is utilized to determine the information rate of discrete Sources Consider Two Messages A Dog bites a man A man bites a dog

  31. Thank You